1. Field of the Invention
The present invention relates to a waterproof camera, and more particularly to a waterproof camera in which an imaging lens is mounted on a camera body and a lens mount mechanism therefor.
2. Related Background Art
A lens mount mechanism for an exchangeable lens of a waterproof camera is disclosed in Japanese patent publication No. 39- 5519. A waterproof camera having a structure shown in FIG. 14 which is a rear lid open/close type with the known lens mount mechanism has also been known. In FIG. 14, a drive mechanism unit 171 is housed in an outer housing 172 so that it is not affected even if the outer housing 172 is deformed by a pressure, and a clearance between the outer housing 172 and a rear lid 173 rotatably pivoted thereto is sealed against water by an O-ring 174. A mount 175 on which a lens inner tube 177 which holds the lens is provided on the drive mechanism unit 171. An opening 172a is provided on a front plane of the outer housing 172.
On the other hand, an imaging lens bodytube is constructed by a lens outer tube 176 and the lens inner cylinder 177. The lens inner tube 177 comprises an imaging lens 178, a focus adjusting mechanism (not shown) and an iris adjusting mechanism. The lens outer tube 176 is constructed in an anti-pressure and waterproof structure, and a waterproof glass 179 is mounted on a front opening by an O-ring 710 so that it is sealed against water. An O-ring 711 is fitted to a peripheral groove 176a formed in a periphery of a rear opening of the lens outer tube 176. Thus, when the lens bodytube is mounted to the camera body, a clearance between the lens outer tube 176 and the outer housing 172 is sealed against water. A lens mount 712 is fixed to the lens inner tube. The lens mount 712 is supported to be movable along an optical axis by a plurality of shafts 713 mounted on the lens outer tube 176. Compressed coiled springs 714 wound around the shafts 713 bias the lens outer tube 176 to a direction to pull the mount 712. When the lens is mounted, a bayonet 712a of the lens mount 712 engages with bayonet pawls 175a of the body mount 175 and the lens inner tube 77 is champed to the body mechanism 71 by the biasing forces of the compressed coiled springs 714. In this manner, the body mechanism 171 and the lens inner tube 177 are coupled to each other and they are not affected even if the lens outer tube 176 is deformed by the water pressure so that good photographing function is maintained.
However, the prior art waterproof camera described above has the following problems.
(1) Since the fitting area between the lens outer lube 176 and the outer housing opening 172a is of waterproof structure by the O-ring 711 only, if an external force which is transverse to the optical axis and which is larger than the biasing forces of the compressed coiled springs 714 is applied, the lens outer tube will be inclined with respect to the outer housing 172. If an air pressure in the camera is higher than the external pressure and higher than the biasing forces of the compressed coiled springs 714, the lens outer tube 176 will be raised from the outer housing 172. In any of the above cases, the waterproof sealing effect by the O-ring 711 is not perfect and there is a risk of water leakage.
(2) The mounting of the lens mount 712 to the body mount 175 is maintained by the biasing forces of the compressed coiled springs 714. If the lens outer tube 176 is inclined, the pressing forces by the compressed coiled springs 714 are ununiform from point to point and the mounting of the lens mount 712 is unstable. In a recent camera in which electronization is very much introduced and electronic circuits are provided in lens and camera body and signals are transmitted through connectors in the respective mount, the instability of the mounting of the lens mount causes the instability of connection of the connectors. This may cause a malfunction. In order to prevent it, the forces of the compressed coiled springs 714 may be increased so that the lens outer tube 176 is hard to be inclined. However, if the biasing forces of the springs are too large, the body mount 175 is deformed, which will adversely affect to a focusing precision of the imaging lens.
(3) When the lens bodytube is mounted to the camera body, it is difficult to determine whether the lens mount 712 is correctly mounted at the predetermined position relative to the body mount 175 because of a frictional force by the O-ring 711. The connectors for electrically connecting the lens bodytube and the camera body are provided in the mounts in order to transmit various signals therebetween. Accordingly, if the lens bodytube is not correctly mounted at the predetermined position relative to the camera body, a malfunction may occur. If the camera is used in an inperfect mounting condition, the lens bodytube may be dropped off the camera body, which will cause water introduction.